72 



BRITISH BELEMNITES. 



other ways of unusual appearance, the term seems natural enough, though founded in 

 part on accidents of decomposition rather than structure. 



If now we tiu-n to Quenstedt, and examine the figures given in pi. xxvi of his 

 • Cephalopoden ' (1849), we find the ordinary blunt compressed form, with its various inner 

 and outer aspects clearly represented (pi. xxvi, figs. 1 — 7.) Another is given, somewhat 

 longer and less obtuse (pi. xxvi, fig. 8) ; again, one somewhat bowed at the end (pi. xxvi, 

 fig. 11), called B. digitalis acutus ; and a closely allied form (pi. xx\d, fig. 65), 

 which shows traces of lateral furrows, receives the name of B. incurvatus. Finally, a 

 longitudinal section (pi. xxvi, fig. 14 c), and two drawings of the lateral aspect of somewhat 

 larger and more pointed specimens, with ventral and dorso-lateral grooves, complete the 

 series of varieties under the title of B. digitalis tripartitus. Of all these Belemnites, 

 which are found only in the Lias, I have seen examples from Enghsh locahties. Only a 

 very small number correspond strictly to B. irregularis of Schlotheim, but there is a 

 great number and variety comprised within the limits of the additional forms of 

 Quenstedt. The middle term of all the varieties agrees with some specimens which are 

 frequent at Whitby, called B. vulgaris by Young and Bird. I possess only one specimen 

 from Whitby at all approaching to B. digitalis in the extreme bluntness and irregularity 

 of the end, which is obscurely marked by a ventral groove, and is eroded. It was taken 

 from the Upper Lias of Saltwick. 



Belemnites irregularis, Schlotheim. PI. XV, figs. 37, 39. 



Reference. Belemnites digitalis. 'Faure Biguet,' I8I0 (as quoted by Blainville in 

 1827, but disallowed by D'Orbigny, 1860). 

 B. irregularis, Schl. ' Taschenbuch,' p. 70, pi. iii, fig. 2, 1813, and 



'Petref.,' p. 48, No. 5, 1820. 

 B. digitalis, Blainv., p. 88, pi. iii, figs. 5, 6, 1827. 



Voltz, p. 46, pi. ii, fig. 5, 1830. 

 B. irregularis, D'Orbigny, 'Pal. Fr. Ceplial.,' p. 74, pi. iv, figs. 2 — 8, 

 1842. 



B. digitalis et B. digitalis irregularis, Quenstedt, 'Ceph.,' p. 416, pi. xxvi, 

 figs. 1— S, 1849. 



GiuARD. Short, straight, cylindroidal, much compressed ; apex oblique and very 

 lilunt in the adult, often marked by a tubercular and pitted surface, from which vermicular 

 l idges and hollows radiate to a short distance. Apex in younger specimens often sub- 

 tnucronate, in very young examples acute. On most specimens there is one short ventral 

 furrow near the apex ; no dorso-lateral grooves at the apex. 



